Problem: If $4a + 7b = -3$ and $7x + 5y = 8$, what is $56x - 4a - 7b + 40y$ ?
Answer: $= -4a - 7b + 56x + 40y$ $= (-1) \cdot (4a + 7b) + (8) \cdot (7x + 5y)$ $= (-1) \cdot (-3) + (8) \cdot (8)$ $= 3 + 64$ $= 67$